For aesthetic, economic and quality control considerations it is desirable, for certain food products, to stuff the casing to a substantially uniform filled diameter over its entire length. For example, a substantially uniform filled diameter is especially desired for the production of stuffed products which are subsequently sliced and prepackaged for retail sales such as bologna or the like. Machines which slice these products usually are set up to cut a predetermined number of slices for each package, but at retail the packages are sold on a weight basis. Accordingly, it is important for the producer to stuff products of substantially uniform filled diameter so that the predetermined slice count will consistently produce packages of substantially the same weight.
Automatic stuffing machines use casing in the form of a shirred stick so that a plurality of stuffed products or "logs" can be made from a single stick. For example, a shirred stick two feet long may contain upwards of two hundred feet or more of casing. After the stick is loaded onto the machine, the intention is to run the machine continuously until the supply of casing is exhausted. Accordingly, it is important that the stuffed diameter of the logs made during the run remains substantially constant.
Stuffed diameter is determined by several factors such as the extensibility of the casing, its moisture content, the drag on the casing during filling and the stuffing pressure. In Reissue U.S. Pat. No. Re. 30,390, a stuffing machine is disclosed which includes means for continuously stuffing shirred casing to produce logs of substantially constant stuffed diameter. In this system, a sizing disc implanted in the casing serves to circumferentially stretch the casing just prior to stuffing. This circumferential stretch exerts a drag or "holdback" on the casing to insure that the casing stuffs out to the full diameter recommended by the casing manufacturer.
U.S. Pat. No. 4,077,090 discloses an improvement to the system of Re. 30,390 by providing means to adjust the drag at the onset of stuffing. In the '090 Patent, a pressure ring is positioned adjacent the sizing disc which directs the casing through a tortuous path first over the sizing disc and then inward through the pressure ring. By adjusting and then fixing the longitudinal distance between the pressure ring and the sizing disc, the drag on the casing is adjusted. However, once made, the adjustment is fixed and is not altered unless stuffing is stopped. Also, the system must be manually set. This done by manually measuring the circumference of the first several stuffed pieces or "logs". The operator then makes a manual adjustment to increase or decrease holdback as needed to provide the correct stuffed diameter.
Periodically during stuffing, the operator will measure the circumference of a log and will stop the machine to make any adjustment needed to correct for deviations from the desired circumference. Accordingly, while the machine is designed for continuous stuffing, the start-up procedure and any subsequent stuffed diameter correction require stopping the machine. This detracts from the economic benefits of continuous operation. Stopping the machine also allows sections of deshirred casing to lose moisture during the interval that the machine is stopped and these sections may have different stuffing properties than casing sections of higher moisture.
Various systems are known for automatically adjusting the drag on the casing during the stuffing cycle to reduce the need for stopping the stuffing operation.
In these systems, means are provided for monitoring the stuffed product in order to obtain feed back information which is then applied to means for adjusting the drag on the casing. For example, in U.S. Pat. No. 4,558,488 the stuffed log passes through the annulus of a calibrating ring. The proximity of the log surface to the inner surface of the ring creates a pneumatic back pressure which is sensed as an indication of the diametrical size of the log. In U.S. Pat. No. 3,148,408 the log moves passed a shoe pivoted towards the log surface. Movement of this shoe is used as an indication of the stuffed diameter.
In a copending application Serial No. 07/039197 now U.S. Pat. No. 4,766,645, the diameter or width of the stuffed log is monitored by shoes which are urged against diametrically opposite sides of a stuffed log traveling between the shoes. The shoes are independently suspended so each can move relative towards or away from a diametrically opposite shoe. The suspension system for the shoes as shown in said copending application includes a plurality of separate parallel motion linkages each associated with a single shoe. Each separate parallel motion linkage inturn is operatively associated with an encoding device. The encoding device is a signal generator which issues an electric signal representative of the movement of its associated parallel motion linkage. While this system is functional, having completely independent suspension systems cause a duplicity of components and crowds the area around the log where the suspension system is mounted. The present invention is an improved suspension system. In particular, the present invention includes an arrangement which allows separate parallel motion linkages and signal generators to share components. This eliminates duplicity of the shared components and simplifies the suspension system.
Accordingly, it is an object of the present invention to provide an improved parallel motion system for suspending shoes to monitor the stuffed diameter of casing and for linking the shoes to a signal generator.
Another object of the invention is to provide a system for measuring the width or diameter of an object by pressing independently mounted shoes against diametrically opposite sides of the object wherein the shoes are mounted on parallel motion linkages utilizing shared mounting component.